I also use the Dremel to clean the threads of screws. Even though no one will ever notice these screw threads when they are turning the knobs of a radio, I clean them any ways. It just takes a few moments with the Dremel to get the results you see here.
In the photograph on the left is an old set screw that has some rust on it as well as a number of burrs in the slot that are left over from a screwdriver. The first thing I do is clean all the rust off the top of the screw and the threads using the Dremel. Now I have a clear picture of the set screw and any damage that has occurred to the screwdriver slot.
The picture on the left also shows the Dremel tool attachment that I use to clean out the screwdriver slot and remove any old burrs. I carefully insert the Dremel tool attachment into the slot of the screw to both clean it and to remove any old burrs. This task can be done with a file, but in my opinion it is so much more easily accomplished with the Dremel tool. It takes just a few seconds and your done. I have not thrown away the files though and use them for delicate work such as on screw heads that have been put through the bluing process, namely on firearms.
The photograph on the right is a before and after picture of the cleaning and de-burring process.